unleashed-firmware/applications/external/totp/lib/base32/base32.c

// Base32 implementation
//
// Copyright 2010 Google Inc.
// Author: Markus Gutschke
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "base32.h"

size_t base32_decode(const uint8_t* encoded, uint8_t* result, size_t bufSize) {
    int buffer = 0;
    int bitsLeft = 0;
    size_t count = 0;
    for(const uint8_t* ptr = encoded; count < bufSize && *ptr; ++ptr) {
        uint8_t ch = *ptr;
        if(ch == ' ' || ch == '\t' || ch == '\r' || ch == '\n' || ch == '-') {
            continue;
        }
        buffer <<= 5;

        // Deal with commonly mistyped characters
        if(ch == '0') {
            ch = 'O';
        } else if(ch == '1') {
            ch = 'L';
        } else if(ch == '8') {
            ch = 'B';
        }

        // Look up one base32 digit
        if((ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z')) {
            ch = (ch & 0x1F) - 1;
        } else if(ch >= '2' && ch <= '7') {
            ch -= '2' - 26;
        } else {
            return 0;
        }

        buffer |= ch;
        bitsLeft += 5;
        if(bitsLeft >= 8) {
            result[count++] = buffer >> (bitsLeft - 8);
            bitsLeft -= 8;
        }
    }
    if(count < bufSize) {
        result[count] = '\000';
    }
    return count;
}